It happens ever so often. When driving for many miles with my air con blowing cold my 05 GTO hesitates or hits a miss then then quits blowing cold air my temperature gauge quits too. It will stay like this until I park it and let it set. I get back in it and everything works good again. Been told it was the ETC sensor but I changed it out and still does it. I have spent much $ trying to figure this symptom out. Been put on the computer to check the codes but cannot seem to fix it. I was asked if I used additives I said yes one fellow checked with his computer and says it is burning too rich quit using them.